Titan was discovered on March 25, 1655 by the Dutch astronomer Christian Huygens, making it one of the first non-terrestrial moons to be discovered.

Titan is the only known moon with a fully developed atmosphere that consists of more than just trace gases; in fact, Titan'satmosphere is denser than Earth's, with a surface pressure more than one and a half times that of Earth.

These hydrocarbons are thought to form in Titan's upper atmosphere in reactions resulting from the breakup of methane by the Sun'sultraviolet light, producing a thick orange smog, and Titan's surface may be coated in a tar-like layer of organic precipitate.

The glow of Titan's extensive atmosphere shines in false colors in this view of Saturn's gas-enshrouded moon acquired by the Cassini spacecraft visual and infrared mapping spectrometer during the July 2, 2004, flyby.

This image of Titan was taken by the Pioneer 11 spacecraft on September 3, 1979 from a range of 3.6 million km.

This much is speculated: the presence of methane oceans and rivers; a layer of surface dust caused by settling smog; bedrock composed of water ice; and as with the moons of Jupiter, Titan's mountains are probably modest in height.

While no one is recommending human travel to Titan anytime soon, Griffith and her colleagues hope the Cassini space probe, due to arrive in 2004, will serve well as a scientific stand-in, furthering our knowledge of the odd moon.

Was released from Cassini on December 24 and landed on Titan January 14.

Jean-Jacques Dordain, director general of the European Space Agency, which led the Huygens mission to Titan, exclaimed "magnifique" as the first image was displayed on screens at ESA mission control in Darmstadt, Germany.

In various instances now we know that ring structures in the Jovian planets are stabilized by small "shepherd moons" that orbit in or near the rings and stabilize them by their gravitational influences.

Titan is hard to study, veiled by a dense hydrocarbon haze that forms in the high stratosphere as methane is destroyed by sunlight.

The by-products of methane molecules destroyed in the sun'sultraviolet light react with other molecules in Titan'satmosphere, forming organic droplets and particulates that fall onto the moon's surface, blanketing the icy bedrock and forming lakes and oceans, Griffith and her colleagues believe.